Helicopter with folding rotor arms

ABSTRACT

A rotary wing aircraft apparatus includes a body and a rotor pair connected to the body by an arm. The rotor pair has an upper rotor driven by an upper motor and rotating about an upper rotor axis and a lower rotor driven by a lower motor and rotating about a lower rotor axis. The upper and lower rotor axes are tilted with respect to each other. Tilting the axes away from the arm increases the distance from the rotor blades to the arm, and decreases the risk of the blades of the rotor contacting the arm. In an aircraft with a plurality of arms extending from the body, and a rotor assembly connected to each arm, the arms can be pivoted from a flying position, where the arms extend laterally outward to a folded position where the arms are positioned substantially parallel and adjacent to each other.

This invention is in the field of rotary wing aircrafts or helicoptersand more particularly rotary wing aircrafts with folding rotor arms.

BACKGROUND

Helicopters using horizontal rotors have been known for a long time.They allow an aircraft to move vertically (allowing vertical take-offs),hover in the air, move side to side, etc. The use of horizontal rotorsgives helicopters an unprecedented amount of movement in relation to afixed wing craft.

However, conventional helicopters are typically very complex. Mostconventional helicopters use a large horizontal rotor for lift and asmaller vertical rotor (the tail rotor) to counterbalance torque imposedon the helicopter by the rotation of the large lift rotor. By alteringthe pitch of the blades of the small vertical rotor, the entirehelicopter can be pivoted from side to side or held straight.

The horizontal rotor must also be specially designed to cause thehelicopter to tilt in different directions when required and to controlthe amount of lift created by the rotors. In one common conventionalsystem, a swash plate assembly, comprising a fixed swash plate and arotating swash plate, is used to change the pitch angle of the rotorblades. The swash plate assembly can be used in two ways: to change thepitch angle of all of the rotor blades collectively; or, by changing thepitch angle of the rotor blades individually and cyclically as theyrevolve. By changing the pitch angle of all of the rotor bladescollectively, the amount of lift generated by the helicopter can beincreased or decreased causing the helicopter to ascend or descend,respectively. By changing the pitch angle of the rotor blades cyclicallyas they revolve, the lift created on one side of the rotor can beincreased causing the helicopter to tilt in a desired direction andthereby move in the direction the helicopter is tilting.

Tandem coaxial rotors have been developed to avoid the use of a smallervertically mounted rotor. A pair of horizontal rotors rotating inopposite directions around a single axis are used. The counter-rotatingpair of horizontal rotor blades can be used to balance out the torquecreated around the single axis by each of the two rotors and by alteringthe speeds of the two rotors relative to each other, the helicopter canbe yawed left or right around the axis shared by the rotors.

While these tandem coaxial rotors remove the necessity for a tail rotor(vertical rotor) to counterbalance the rotational forces placed on ahelicopter by a single rotor, to achieve all the desired movements of aconventional helicopter helicopters with tandem coaxial rotors haveincreased the mechanical complexity of the rotor systems. Rather than inmore conventional systems which use two swashplates in the swashplateassembly to change the pitch of the rotor blades, tandem coaxial rotorstypically use two swashplates for each rotor requiring four swashplatesto be needed. In addition, provisions typically have to be made for thecontrol system of the upper rotor to pass through the lower rotorcontrol system.

While some remote controlled helicopters such as toys and drones haveused simple versions of tandem coaxial rotor systems, they have oftensacrificed the range of producible movements in order to reduce themechanical complexity of the rotor system.

It is desirable in many applications to have a helicopter that canachieve all the movements of a conventional helicopter with a reducedmechanical complexity. It is also desirable to have a helicopter thatcan be folded into a relatively compact form for transport.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a rotary wingaircraft apparatus with upper and lower rotors that overcomes problemsin the prior art.

The invention provides, in a first embodiment, a rotary wing aircraftapparatus comprising a body and a rotor pair connected to the body by anarm. The rotor pair comprising an upper rotor driven by an upper motorand rotating about an upper rotor axis and a lower rotor driven by alower motor and rotating about a lower rotor axis. The upper and lowerrotor axes are tilted with respect to each other. Tilting the axes awayfrom the arm increases the distance from the rotor blades to the arm,and decreases the risk of the blades of the rotor contacting the arm.

The invention provides, in a second embodiment, a rotary wing aircraftapparatus comprising a body, a plurality of arms extending laterallyfrom the body, and a rotor assembly connected to an outside end of eacharm. The arms are connected to the body such that the arms can bepivoted from a flying position, where the arms extend laterally outwardfrom the body such that the rotor assemblies are spaced in a desiredconfiguration, to a folded position where the arms are positionedsubstantially parallel and adjacent to each other. The folded aircraftis comparatively compact and easier to transport, and in the compactform the aircraft is less susceptible to damage.

In one embodiment the aircraft has two forward arms supporting rotorarms that can be folded to lie adjacent to a rear extending armsupporting a coaxial rotor pair. In this position, the aircraft can beloaded into a pneumatic cannon or other propulsion device and quicklylaunched to a desired altitude where the forward arms will rotateforward and the aircraft can be flown starting from the desiredaltitude.

DESCRIPTION OF THE DRAWINGS

While the invention is claimed in the concluding portions hereof,preferred embodiments are provided in the accompanying detaileddescription which may be best understood in conjunction with theaccompanying diagrams where like parts in each of the several diagramsare labeled with like numbers, and where:

FIG. 1 is perspective view of an aircraft;

FIG. 2 is a top view of the aircraft shown in FIG. 1;

FIG. 3 is a perspective view of one rotor pair of the aircraft shown inFIG. 1;

FIG. 4 is a side view of the rotor pairs shown in FIG. 3;

FIG. 5 is a side view of the rotor pair shown in FIG. 3 with the rotorblades turned to show the pitch angle of the rotor blades; and

FIG. 6 is a schematic top view of an aircraft in a flying position inanother aspect; and

FIG. 7 is a schematic top view of the aircraft of FIG. 6 in a foldedposition;

FIG. 8 is a perspective view of a mechanism for folding the arms of theaircraft, with the arms in the folded position;

FIG. 9 is a top view of the mechanism of FIG. 8, with the arms in thefolded position;

FIG. 10 is a perspective view of the mechanism of FIG. 8, with the armsin the flying position;

FIG. 11 is a top view of the mechanism of FIG. 8, with the arms in theflying position;

FIG. 12 is a side view of an alternate rotor pair of the presentinvention where the upper and lower rotor axes are tilted away from thearm;

FIG. 13 is a perspective rear view of an alternate aircraft with fourarms and rotor pairs in the flying position;

FIG. 14 is a perspective rear view of the aircraft of FIG. 13 in thefolded position;

FIG. 15 is a bottom view of the aircraft of FIG. 13 in the flyingposition with the bottom plate removed;

FIG. 15A is a top view of the removed bottom plate in FIG. 15;

FIG. 16 is a bottom view of the aircraft of FIG. 13 in the foldedposition with the bottom plate removed;

FIG. 16A is a top view of the removed bottom plate in FIG. 16.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

FIGS. 1 and 2 illustrate an aircraft 100 with three coaxial rotor pairs110. Using the three coaxial rotor pairs 110, aircraft 100 is capable ofperforming the maneuvers a typical conventional helicopter is capableof, yet does not require the mechanical complexity of a typicalconventional helicopter and all of the coaxial rotor pairs 110 can beused to create lift.

Each of the rotor pairs 110 are positioned at the end of an arm 120connected to a main body 130 of the aircraft 100. In an aspect, the arms120 are positioned extending at regular intervals around a central axis,CA, with each arm 120 positioning the rotor pair 110 attached to the endof the arm 120 the same distance away from the central axis, CA, as theother rotor pairs 110 and with each arm 120 positioned so the rotorpairs 110 are positioned at the corners of an equilateral triangle, asillustrated in the top view of FIG. 2.

FIG. 3 illustrates a perspective view of one of the rotor pairs 110. Therotor pair 110 has an upper rotor 210 and a lower rotor 220. The upperrotor 210 and lower rotor 220 each have two rotor blades 230 that rotatearound a rotor axis, RA.

In operation, when the upper rotor 210 and lower rotor 220 are rotatedto generate lift, the upper rotor 210 and lower rotor 220 rotate inopposite directions around the shared rotor axis, RA. The rotation ofthe upper rotor 210 around the rotor axis, RA, causes the rotor pair 110to want to rotate around the rotor axis, RA. However, thecounter-rotation of the lower rotor 220 around the rotor axis, RA,causes the rotor pair 110 to want to rotate in the opposite directionaround the rotor axis, RA. By altering the speeds of rotation of theupper rotor 210 and the lower rotor 220 and changing the rotationalspeed differential between the upper rotor 210 and the lower rotor 220,the rotational forces created by the rotating upper rotor 210 and lowerrotor 220 can be balanced or used to create a torque effect in a desireddirection around the rotor axis, RA.

Particularly when the aircraft 100 is a small remote control aircraft,such as toys, hobby devices or unmanned drones, each upper rotor 210 andlower rotor 220 can be independently driven by its own electric motor245 with the upper rotor 210 attached to the output shaft 250 of theelectric motor 245 and the lower rotor 220 attached to the output shaft250 of the electric motor 245. The speed of the upper rotor 210 andlower rotor 220 can be varied independently of the each other by varyingthe current being directed to the corresponding electric motor 245.

FIG. 4 illustrates a side view of a rotor pair 110. First ends 232 ofthe rotor blades 230 making up the upper rotor 210 and lower rotor 220are fixedly connected to shafts 250 running along the rotor axis, RA,causing the rotor blade 230 to remain substantially perpendicular to therotor axis, RA, when the shafts 250 are rotated. When the aircraft 100is at rest on the ground, the rotor blades 230 are positionedsubstantially horizontally.

When the aircraft 100 is in flight, the upper rotor 210 rotates througha first plane, A that is substantially perpendicular to the rotor axis,RA, and the lower rotor 220 rotates through a second plane, B that isalso substantially perpendicular to the rotor axis, RA causing planes Aand B defined by the rotating upper rotor 210 and lower rotor 220,respectively, to remain substantially parallel to each other.

FIG. 5 illustrates a side view of a rotor pair 110. In an aspect, apitch angle PA1 of the rotor blades 230 of the upper rotor 210 and a thepitch angle PA2 of the rotor blades 230 of the lower rotor 220 remainfixed relative to the rotor axis, RA.

In an aspect, the rotor blades 230 are sufficiently rigid so that theywill not bend or twist when the aircraft 110 is in flight.

Referring again to FIGS. 1 and 2, the fixed upper rotors 210 and fixedlower rotors 220 allow the aircraft 100 to be manufactured with very fewmoving parts yet still maintain all of the movements of conventionalhelicopters. Rather than having a number of varying mechanical linkagesconnecting each of the rotors to vary the pitch angle of the rotorblades or the pitch of the rotors, only the electric motors 245 aremoving with the upper rotors 210 and the lower rotors 220 rigidlyconnected to output shafts 250 of the electric motors 245.

The aircraft 100 can increase or decrease altitude by increasing ordecreasing the speed of rotation of all of the upper rotors 210 and allof the lower rotors 220 at the same time. By increasing the speed ofrotation of all of the upper rotors 210 and all of the lower rotors 220the lift generated by all of the rotor pairs 110 is increased and theaircraft 100 can be made to rise vertically. Additionally, by decreasingthe speed of rotation of all of the upper rotors 210 and all of thelower rotors 220, the altitude of the aircraft 100 can be decreased. Inthis manner, all six rotors making up the rotor pairs 100 can be used togenerate vertical lift with none of the engine(s) capacity beingdirected to horizontal rotors.

The aircraft 100 can also be moved horizontally in any direction. Tomove the aircraft 100 in a desired horizontal direction, the speed ofrotation of one or more rotor pairs 110 on a side of the aircraft 100facing the desired direction are decreased or the speed of rotation ofthe other rotor pairs 110 can be increased. This will cause the aircraft100 to tilt towards the desired direction of travel, tilting all of theupper rotors 210 and all of the lower rotors 220 downwards towards thedesired direction and creating some horizontal thrust. This horizontalthrust causes the aircraft 100 to move in the desired direction. Themore the one or two rotor pairs 110 are slowed or the more the otherrotor pair(s) 110 speed of rotation is increased, the greater the tiltof the aircraft 110 and the faster the aircraft 100 will travel in thedesired direction.

The aircraft 100 can be yawed so that it rotates around the centralaxis, CA, either to the right or to the left by decreasing the speed ofrotation of the upper rotors 210 and lower rotors 220 rotating oppositeto the desired direction of yaw, increasing the speed of rotation of theupper rotors 210 and lower rotors 220 rotating in the desired directionof yaw or both decreasing the speed of rotation of the upper rotors 210and lower rotors 220 rotating opposite the desired direction of yaw andincreasing the speed of rotation of the upper rotors 210 and lowerrotors 220 rotating in the desired direction of yaw.

In this manner, the aircraft 100 can be made to rise, descent, travel inany horizontal direction and yaw right or left in the same manner as aconventional helicopter without requiring the complex mechanicallinkages required in a conventional helicopter.

FIGS. 6 and 7 illustrate the aircraft 100 in a further aspect. Theaircraft 100 has a body 130, and a plurality of arms 120 extendinglaterally from the body 130, and a rotor pair 110 connected to anoutside end of each arm 120. The arms 120 are connected to the body 130such that the arms 120 can be pivoted from a flying position illustratedin FIG. 6, where the arms 120 extend laterally outward from the body 130such that the rotor pairs 110 are spaced in a desired configuration, toa folded position illustrated in FIG. 7 where the arms 120 arepositioned substantially parallel and adjacent to each other.

While the illustrated aircraft 100 uses rotor pairs 110 as illustratedwith upper and lower rotor 210, 220, it is also contemplated that anaircraft using a rotor assembly with only a single rotor mounted on thearms 120 could also utilize the folding arm feature of the presentinvention.

Aircraft 100 has two arms 120A, 120B supporting rotor pairs 110A, 110Bextending to the sides and slightly forward of the body 130 of theaircraft 100 and arm 120C supporting rotor pair 110C extending to therear of the body 130. The two front arms 120A, 120B supporting rotorpairs 110A, 110B are pivotally attached to the body 130 of the aircraft100 and the ends of the arms 120A, 120B opposite to the ends supportingthe rotor pairs 110A, 110B, so that the front arms 120A, 120B can bepivoted rearwards of the body 130 of the aircraft 100 so that the arms120A, 120B are positioned adjacent the rear extending arm 120C, as shownin FIG. 7. The rotor blades 230 can then be rotated so that they runsubstantially parallel to the arms 120A, 120B, and 120C.

FIGS. 8-11 illustrate one folding mechanism for folding the arms 120together. The body 130 is shown in phantom lines. A clip bracket 161 isfixed to the inner end of arm 120C and a resilient clip 163 is mountedon each end of the clip bracket 161.

The arms 120A, 120B are pivotally attached at their inner ends toopposite ends of a pivot bracket 165 attached to the arm 120C a shortdistance from the clip bracket 161. The clips 163 and pivot bracket 165are configured such that the arms 120 can fold together as illustratedin FIGS. 8 and 9 for storage, and such that the arms 120A, 120B can bepivoted outward to ward their corresponding clips 163A, 163B. The armscan be pushed into the clips 163 to open the clips and allow the arms120 to fully engage the clips 163, which will then close and lock thearms 120A, 120B in the position illustrated in FIGS. 10 and 11.

Although it is contemplated that other clip configurations could beused, the illustrated clips 163 comprise resilient upper and lower cliplegs 167 configured such that when the rounded arm 120 contacts the clip163, the clip legs 167 are forced correspondingly up and down such thatthe arm 120 can move into upper and lower grooves 169 in the upper andlower clip legs 167 and such that the legs 167 then move together tomaintain the arm 120 in the grooves 169.

The clips 163 are oriented on the clip bracket 161 so that when the arms120A, 120B are engaged in their corresponding clips 163A, 163B, therotor pairs 110 will be in their desired positions equally spaced aboutthe central axis CA.

In this folded position the aircraft 100 can be launched from alaunching mechanism such as a pneumatic cannon, etc. into the air toachieve an initial altitude. From this initial altitude, the front arms120A, 120B can be rotated forward into their flying position, the rotorpairs 110 engaged so that the upper rotors 210 and lower rotors 220 arerotating, and the aircraft 100 can then be flown starting from thisinitial altitude the aircraft 100 has been launched to.

The front arms 120A, 120B could be motor driven so that a small motorpivots the front arms 120A, 120B forward into the flying position.Alternatively, in the mechanism illustrated in FIGS. 8-11 the front arms120A, 120B can be biased towards the front of the aircraft 100 and theflying position, such as by coil springs 171 wrapped around the pivotpins pivotally attaching the front arms 120 A, 120B to the pivot bracket165. In this manner, the front arms 120A, 120B can be held adjacent tothe rearward extending arm 120C in the launching mechanism, and once thefront arms 120A, 120B are freed from the launching mechanism the biasforce would push the front arms 120A, 120B forward into engagement withthe clips 163 and in their flying position allowing the aircraft 100 tobegin to fly using the rotor pairs 110.

In this manner, aircraft 100 can be quickly launched to a desiredaltitude over a desired area and then once in the flying position flownlike a helicopter. Alternatively where no launcher is being used, thefront arms 120A, 120B could still be biased and held in the foldedposition by a retainer, such that releasing the retainer will cause thefront arms 120A, 120B to move automatically to the flying position.

FIGS. 13-16 illustrate an alternate embodiment of the folding armaircraft 500 comprising four rotor pairs 510, each rotor pair 510attached to the body 530 by an arm 520. Each arm 520 is positionedapproximately ninety degrees around a central axis CA from an arm 520supporting an adjacent rotor pair 510. Right and left front arms 520RF,520LF extend forward and to sides of the body 530 and right and leftrear arms 520RR, 520LR extends rearward and to sides of the body 530when the aircraft is in a flying position as illustrated in FIGS. 13 and15. In this aircraft with four arms, all arms 520 are pivotally attachedto the body 530 such that the right and left rear arms 520RR, 520LR canbe pivoted rearward to a folded position extending rearward, and thenthe right and left front arms 520RF, 520LF can be pivoted rearward to afolded position extending rearward with one front arm on each side ofthe folded rear arms 520RR, 520LR and substantially parallel to andadjacent to the rear arms 520RR, 520LR as illustrated in FIGS. 14 and16.

As can be seen in the bottom view of the body 530 with the bottom plate571 removed in FIGS. 15 and 15A, the right and left rear arms 520RR,520LR are pivotally mounted to the body at rear pivot locations RPAadjacent to each other, and the right and left front arms 520RF, 520LFare pivotally mounted to the body at front pivot locations FPA forwardof and laterally spaced from the rear pivot locations RPA.

As can be seen in FIG. 15, the arms 520 engage clips 563 mounted to thebody 530 to keep the arms 520 in the flying position. The front clips563F can be fixed to the body 530 however the rear clips 563R must bemoved up into the body 530 so that the front arms can move rearward pastthe rear clips 563R as shown in FIG. 16. The clips 563R can be movedmanually, or could also be biased downward so that when the front arm520F is folded back it forces the rear clip 563R up into the body 530.It is contemplated that numerous other clip configurations or likemechanisms could be used as well. Since the aircraft are relativelylight, and the forces exerted by the rotors 510 is relatively small, itis also contemplated that the arms 520 could bear against the body 530and the bottom plate 571 such that friction of the arms 520 between thebody 530 and bottom plate 571 prevents movement of the arms 520 duringoperation but allows manual movement of the arms between the flying andfolded positions.

Such rotary wing aircraft with pairs of upper and lower rotors connectedto the aircraft by a lateral arm can be beneficially used forsurveillance. A camera can be mounted to the bottom of the body 130 withimages stored or sent by wireless transmission to a receiver. The lowerrotor 220 can interfere with the camera view downward and laterally,decreasing the available camera viewing angle. For this reason it isdesirable to have the upper and lower rotors 210, 220 as verticallyclose together as possible. Since the rotor blades 230 are somewhatflexible, they bend and flex as air and power conditions vary. It istherefore not possible to mount the rotor blades 230 very close to thearm 120, as the blades must be kept a sufficient distance above andbelow the arm 120 to avoid contact with the arm 120.

In the rotor pair 110 illustrated in FIG. 4 above, the upper and lowerrotors 210, 220 rotated about a common axis RA, which axis wasperpendicular to the arm 120. FIG. 12 illustrates an alternate rotorpair 310 connected to an aircraft body as above by an arm 420. Eachrotor pair comprises an upper rotor 410 driven by an upper motor 445 androtating about an upper rotor axis RA and a lower rotor 420 driven by alower motor 445 and rotating about a lower rotor axis RA′ that is notaligned with the upper rotor axis RA. Unlike the rotor pair 110 of FIG.4, in the rotor pair of FIG. 12 the upper and lower rotor axes RA, RA′are tilted with respect to each other. The axes RA, RA′ both tilt awayfrom the arm 120 such that outer ends of blades 430 of the upper rotor410 are farthest away from blades 430 of the lower rotor 420 when theypass the arm 120.

Thus the outer ends of the rotor blades 430 are raised with respect tothe arm 420 and are farther away from the arm 120 than in the embodimentshown in FIG. 4, and somewhat closer together in the portion of therotation opposite the arm 120, where there is no arm to interfere withthe blades. A small tilt angle N can move the blades sufficiently, andthe angle N must not be so large that there is a risk the upper andlower blades will touch in the portion of the rotation opposite the arm120.

Since the upper and lower rotor blades are driven in opposite directionsby separate motors 445, it is only required to provide a wedge shapedmounting member 475 between the upper and lower motors 445 to achievethe required tilt. It is contemplated that any helicopter with upper andlower rotor blades mounted on an arm could benefit from the tilted rotoraxis arrangement of FIG. 12 to reduce the risk of contact between theblades and the arm. The blades are quite light and tend to flex whenexerting lifting forces as they rotate through the air. This forcecauses the blades to flex in response, such that the blades can contactthe arm. It is also known to mount the rotor blade to the motor shaftabout a horizontal pivot axis oriented perpendicular to the axis of theblade so the blade can rock. This configuration can reduce vibration,but also increases the risk of the blade contacting the arm. Tilting therotor blades away from the arm as in the present invention reduces therisk of such contact.

The foregoing is considered as illustrative only of the principles ofthe invention. Further, since numerous changes and modifications willreadily occur to those skilled in the art, it is not desired to limitthe invention to the exact construction and operation shown anddescribed, and accordingly, all such suitable changes or modificationsin structure or operation which may be resorted to are intended to fallwithin the scope of the claimed invention.

1. A rotary wing aircraft apparatus comprising: a body; a plurality ofarms extending laterally from the body, and a rotor assembly connectedto an outside end of each arm; wherein the arms are connected to thebody such that the arms can be pivoted from a flying position, where thearms extend laterally outward from the body such that the rotorassemblies are spaced in a desired configuration, to a folded positionwhere the arms are positioned substantially parallel and adjacent toeach other.
 2. The apparatus of claim 1 comprising a clip configured toreleasably engage at least one arm when the at least one arm is in theflying position and wherein the clip is mounted such that the at leastone arm is secured in the flying position.
 3. The apparatus of claim 2wherein the clip is mounted on the body or on one of the plurality ofarms.
 4. The apparatus of claim 3 wherein the clips comprise resilientupper and lower clip legs configured such that when a rounded armcontacts the clip the clip legs are forced correspondingly up and downsuch that the arm can move into upper and lower grooves in the upper andlower clip legs and such that the legs then move together to maintainthe arm in the grooves
 5. The apparatus of claim 1 wherein at least onearm is biased, when in the folded position, towards the flying positionand a retainer is used to hold the at least one arm in place in thefolded position.
 6. The apparatus of claim 1 comprising three rotorassemblies each attached to the body by an arm, each arm positioned sothe rotor assemblies are positioned substantially at the corners of anequilateral triangle.
 7. The apparatus of claim 6 wherein right and leftfront arms extend to the sides of the body and a rear arm extendsrearward from the body when the apparatus is in a flying position. 8.The apparatus of claim 7 wherein the right and left front arms arepivotally connected to the body such that the right and left front armscan be pivoted rearward to a folded position where the right and leftside arms are positioned substantially parallel to and adjacent to therear arm.
 9. The apparatus of claim 8 wherein the right and left frontarms are biased towards the flying position and a retainer is used tohold the right and left arms in place in the folded position.
 10. Theapparatus of claim 8 comprising a clip bracket extending laterally rightand left from a front end of the rear arm, and right and left clips oncorresponding right and left ends of the clip bracket, and wherein theclip bracket is configured such that the right and left front arms arereleasably engaged in the corresponding right and left clips when in theflying position.
 11. The apparatus of claim 10 comprising a pivotbracket extending laterally from the rear arm at a location removed fromthe rear end of the rear arm, and wherein the right and left front armsare pivotally attached to corresponding right and left portions of thepivot bracket.
 12. The apparatus of claim 10 wherein the clips compriseresilient upper and lower clip legs configured such that when a roundedarm contacts the clip the clip legs are forced correspondingly up anddown such that the arm can move into upper and lower grooves in theupper and lower clip legs and such that the legs then move together tomaintain the arm in the grooves.
 13. The apparatus of claim 1 comprisingfour rotor assemblies, each rotor assembly attached to the body by anarm, each arm positioned approximately ninety degrees around a centralaxis from an arm supporting an adjacent rotor assembly.
 14. Theapparatus of claim 13 wherein right and left front arms extend forwardand to sides of the body and right and left rear arm extends rearwardand to sides of the body when the apparatus is in a flying position. 15.The apparatus of claim 14 wherein the right and left front and rear armsare pivotally connected to the body such that the right and left reararms can be pivoted rearward to a folded position extending rearward,and the right and left front arms can be pivoted rearward to a foldedposition extending rearward with one front arm on each side of thefolded rear arms and substantially parallel to and adjacent to the reararms.
 16. The apparatus of claim 15 wherein the right and left rear armsare pivotally mounted to the body at rear pivot locations adjacent toeach other, and the right and left front arms are pivotally mounted tothe body at front pivot locations forward of and laterally spaced fromthe rear pivot locations.